Date: Sat, 16 Jan 99 11:28:10 CST From: Dick Campbell Subject: statalist: STATA question on LSMEANS ** Send unsubscribe or help commands to majordomo@hsphsun2.harvard.edu ** LSMEANS in SAS is a bit tricky. The default setup ives you adjusted means assuming orthogonality. That is, if the design is unbalananced, you get an adjusted set of means under an assumption of orthoronality. This has been the default for years. If the design is orthogonal it is of no consequence, but it is a serious issue if you analyze survey data. Many users have not appreciated this, thinking they are getting a standard ANCOVA adjustment when they were getting something rather different. In version 6.12 of SAS the problem has been corrected by allowing an OBSMARGINS statement on LSMEANS which "is reasonable when you want the inferences to apply to a population that is not necessarily balanced bu has the margins observed in your data set." (SAS/STAT Software" Changes and Enhancements trough Release 6.12, p. 353). Note, however, that the default is to assume a balanced design. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Richard T. Campbell Professor of Sociology Director, Research Methods Core Health Research and Policy Centers (HRPC) E-mail: dcamp@uic.edu ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Dept. of Sociology M/C 312 HRPC M/C 275 1007 W. Harrison St. 850 W. Jackson Blvd Chicago IL 60607-7140 Chicago IL 60607-3025 312.413.3759 312.413.0480 FAX: 312.996.5104 FAX: 312.996.2703 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~